One well in the previous set of samples contained arsenic at nine times the safe drinking water limit and did pose a health threat, the agency said, but a resident refused offers of replacement water.

Elevated levels of methane, barium, arsenic and sodium were detected in other wells but the agency said they were either successfully treated or did not pose a health concern. Twenty of the wells had methane above the state's reporting threshold and five of those were at or above the EPA's "trigger level" or the point when dissolved methane begins to escape into the atmosphere.

The agency has said it has not done any detailed review to determine the cause of any contaminants.

The EPA testing is only a snapshot of the highly changeable aquifer and will not be the final word on the health of the water supply. But pro-industry groups and Cabot Oil & Gas Corp., the Houston-based driller whose faulty gas wells were previously found to have leaked methane into the aquifer, assert the test results justify their position that Dimock's water is safe.

"Cabot is pleased that EPA has now reached the same conclusion of Cabot and state and local authorities resulting from the collection of more than 10,000 pages of hard data - that the water in Dimock meets all regulatory standards," spokesman George Stark said Friday.

But residents who are suing Cabot and anti-drilling activists say the EPA has issued a series of misleading statements on what the tests show. They say some of the wells had a combination of chemicals, metals, gases and salts that suggest the influence of drilling and fracking; that drinking-water standards have not been established for some of the toxic substances that turned up in the wells; and that testing also revealed high and sometimes explosive levels of methane in about a third of the wells. Opponents also raised technical concerns about the data.

"The fact remains, EPA's own tests have already vindicated the long-standing allegations of water contamination and clearly shows that the water of the affected residents is unfit for human consumption," said Claire Sandberg, executive director of Water Defense, an anti-drilling organization.

EPA will resample four wells where earlier testing by Cabot and the Pennsylvania Department of Environmental Protection showed unsafe levels of contaminants.

Dimock residents sued Cabot in 2009. It now appears they are in settlement talks with the company, AP says.

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About Doug Stanglin

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